Method and apparatus for solution mining



2 Sheets-Sheet l J. W. CURRIER METHOD AND APPARATUS FOR SOLUTION MINING Jan. 10, 1967 Filed June 24 Jan. 10, 1967 J. w. CURRIER 3,297,362

METHOD AND APPARATUS FOR SOLUTION MINING Filed June 24, 1963 2 Sheets-Sheet 2 F'IELE United States atent 3,297,362 METHOD AND APPARATUS FOR SOLUTION MINING James W. Currier, Palatine, Ill., aignor to International Minerals & Chemical Corporation, New York, N.Y., a corporation of New York Filed June 24, 1963, Ser. No. 289,919 7 Claims. (Cl. 299-5) This invention relates to a method and apparatus for the solution mining of soluble minerals. More particularly, this invention relates to a method and apparatus for which improved fluid distribution in a subterranean cavity is obtained. In another aspect, this invention relates to an improved method and apparatus for forming subterranean Caverns for the storage of fluid materials by the removal of soluble formation constituents.

It has been proposed to recover valuable minerals from deeply buried deposits by dissolving the mineral in a solvent, usually Water, which is circulated through a wellbore from the surface of the earth into the mineral-bearing deposit, and thence upward through the same or different well-bore to the surface of the earth. It has usually been preferred to drill a single well into the mineralbearing deposit, and equip the well to provide two conduits which terminate at vertically spaced points Within the formation. An unsaturated solvent is pumped downward through the well to dissolve soluble minerals from the formation, and more highly concentrated solvent is pumped from the formation to the surface of the earth. A portion of the dissolved mineral content of the solvent is then recovered, usually by reducing the temperature of the solvent.

As the material is dissolved and removed from the subterranean formation, a cavern or cavity is formed. As the size of the cavity increases unsatisfactory circulation of solvent within the cavity has been found to exist. Flow rates adjacent the wall of the cavity are too low, the bulk of the fresh solvent tending to follow the shortest path between the outlet of the input conduit and the inlet of the output conduit.

It is an object of this invention to provide a method and apparatus whereby improved circulating eiiciency is obtained in cavities formed by solution mining.

Another object of this invention is to provide a method and apparatus for solution mining whereby flow of solvent is directed in a path closely paralleling the walls of a subterraneancavity.

Another object of this invention is to provide a method and apparatus for solution mining whereby increased fluid velocities are obtained in solution mining cavities adjacent the walls thereof.

Still another object of this invention is to provide a method for controlling the shape of solution mining cavities.

Briey, the invention resides in utilizing a large bladder or balloon fabricated of a foldable, flexible material which can be inserted through a well casing and into a cavity formed by solution mining. The bladder is disposed between the inlet and outlet of the solvent distribution system and is inflated until it occupies a major portion of the volume of the cavity, whereby the flow of solvent is directed over a course adjacent to the walls of the cavity.

The invention is described in detail with reference to the drawings of which:

FIGURE 1 is a vertical section showing a solution mining assembly in which the apparatus of this invention is incorporated,

FIGURE 2 shows an alternate embodiment of the apparatus of this invention,

Patented Jan. 10, 1967 ICC FIGURE 3 shows a second alternate embodiment of the apparatus of this invention, and

FIGURE 4 is a view of the apparatus shown in FIG- URE 3 taken in the direction 4-4.

Referring to FIGURE 1, a subterranean formation 10 includes a mineral-bearing stratum 12 which lies below an impermeable stratum 14. A well-bore 16, which communicates the mineral-bearing stratum 12 with the surface of the earth, is provided with a conventional well casing 18 and a tubing string 20. The well casing terminates just below impermeable stratum 14, which is to say, adjacentv the top of the mineral-bearing formation 12. Tubing string 20 extends to a greater depth in formation 12, and a salt cavity 22 has developed through the removal of soluble formation constituents. The salt cavity is typical of that formed by circulating a solvent, such as hot water, downward through annulus 24 which lies between the interior of casing 18 and the exterior of tubing string 20. The hot water dissolves a mineral, such as potassium chloride, and the mineral-laden water is removed from cavity 22 upward through tubing string 20.

In accordance with this invention, when the salt cavity has reached such dimensions that solvent circulation is found to follow a course downward from casing 18 to tubing string 20, Without adequately contacting the walls of the subterranean formation, the solution mining system is modified in accordance with this invention. A packer 26 is secured to tubing string 20 at a suitable distance above the low end thereof. The packer 26 is provided with a plurality of apertures 28. A bladder 30, which is fabricated of a foldable, flexible material is secured to the tubing string intermediate packer 26 and the lower end of the tubing string. Fluid communication is provided between the apertures 28 and the bladder interior by securing the bladder to the packer outwardly of the apertures. This can be conveniently done by providing the packer with a tubular shoulder 32 and securing the upper end of the bladder to the shoulder, as shown. The bladder is provided with a plurality of openings such as openings 34 which are preferably spaced circumferentially around the upper portion of the bladder, or in any event are positioned in a portion of the bladder remote from the inlet to tubing string 20.

The bladder may be fabricated of any of a number of thin, substantially fluid impermeable, flexible materials capable of withstanding temperatures normally encountered in solution mining, i.e., temperatures up to about 200 F. Polyethylene lms are suitable, and polyethylene terephthalate films are preferred. Especially preferred are polyethylene terephthalate lms reinforced with nylon web. The nylon web greatly improves the strength and tear resistance of the film, which is preferably bonded to the web.

In operation, when the c-avity has reached a size such that the circulation ei'hciency in the cavity is considered unsatisfactory, tubing string 20 is removed from .the well- Ibore and equipped with a packer and bladded as shown in FIGURE l. The bladder is, however, initially folded into a compact cylindrical form as illustrated, for example, in FIGURE 2. Thus the entire bladder and packer are insertable within the casing, and .the diameter of the Ibladder when folded is preferably sufficiently smaller than the diameter of the packer so that the packer serves as a guide to prevent damage to .the bladder as the assembly is run downward through the casing. After tubing string 2G has been returned to position packer 26 is expanded to provide uid-tight seal between casing 18 and tubing string 20 adjacent the lower extremity of casing 18. It will be understood that packer 26 is merely illustrated schematically, such packers and their operation being well known and understood in the well arts. Bladder 30 is inflated by the circulation of solvent downward through annulus 24, through apertures 2S in packer 26 and into the interior of the bladder. After the bladder has expanded to its maximum diameter .the solvent flows outwardly through openings 34 and circulates as indicated in FIGURE 1. The circulation is thus directed to place the solvent in intimate contact with the walls of the cavity, whereby greater quantities of valuable mineral are dissolved. A further advantage is obtained in that the velocity of the solvent adjacent to the walls of the cavity is maintained at a high level, whereby the rate of solution of salt in the solvent is increased.

Referring now to FIGURE 2 an alternate embodiment of the apparatus is shown. The packer has been eliminated and guide 40, which comprises a ring 42 and a plurality of spokes 44, has been secured to tubing string 46 above folded bladder 48. The function of guide 40 is to prevent contact between folded bladder 48 and the well casing as the tubing string is run downward through the well. A strap 50 is provided to retain the bladder in folded condition and at minimum diameter. In practice a number of such straps will generally `be employed. The strap is fragible and may be fabricated of some easily broken material, such as, a very thin plastic film. Internal pressure within the bladder breaks strap 50 and permits the bladder to inflate. A small, bent pipe 52 having an opening directed axially of the tubing string and communieating with the interior of the -bladder is provided. The bladder is sealed at 54 and 56 in a fluid-type relationship with the tubing string. In operation, the velocity of fluid flow downward through the tubing string creates a velocity head which is communicated to the interior of the bladder. At high rates of solvent ow this kinetic head is sufficient to create a pressure differential between the interior of the bladder and the interior of the cavity. Thus the bladder is forced outwardly by this pressure differential and retained in expanded condition as long as fluid is pumped downward through the tubing string.

Referring to FIGURES 3 and 4, an alternate embodiment of the apparatus is illustrated. In this embodiment the bladder 60 is provided with two radial, vertical, fluidtight partitibns 62 and 64 which together divide the lbladder into two hemispherical segments. YTwo separate fluid inlet conduits 66 and 68 extend internally of tubing string section 70, and communicate with bladder segments 72 and 74, respectively. In use, the bladder segments are folded separately and one of the bladder segments is secured by a fragible strap such as strap 76. After the 'bladder has been positioned in a subterranean cavity, fluid pressure is applied through conduit 66 to inflate segment 72 of bladder 60. Segment 74 of bladder 60 remains in a collapsed condition, but unfolds sufciently to permit expansion of segment 72, as illustrated in FIGURE 4. After further production of soluble minerals from the subterranean formation the cavity will eventually again increase in size to the point at which circulation becomes unsatisfactory because of the excess radial distance between the wall of the partially inflated bladder and the wall of the cavity. Bladder segment 74 is then inflated by applying fluid pressure through conduit 68. The uid pressure causes strap 76 to rupture and segment 74 becomes inflated, whereby the bladder is expanded to its maximum extent It will be understood that an operative device of somewhat more simple construction than is shown in FIG- URES 3 and 4 can be made by merely eliminating the two radial, vertical Huid-tight partitions 62 and 64, and uid inlet conduit 68. In this case, the bladder can be inflated by applying to conduit 66 a pressure great enough to inflate the bladder, but insufficient to cause rupture of strap 76. When required, the thus partially inflated bladder can be increased in size to its full dimensions by applying an increased pressure sufficient in magnitude to rupture strap 76, whereby the bladder is inflated to its maximum dimensions. It is, however, desirable to incorporate in the device the vertical partitions 62 and 64 since this eliminates necessity for controlling the magnitude of the pressure applied to inflate the bladder. Such control can be diicult where the bladder is disposed at great depths due to hydrostatic head considerations. Also, the partitions serve a useful function as restaining members in cylindrically shaped bladders. 1t will be understood that where the top and bottom panels of the bladder are substantially flat or disc-like in shape, internal pressure wil-l tend to bulge these panels to produce a more nearly spherical shape. The partitions 62 and 64 serve to restrain against such deforming of the bladder,

The bladder can be fabricated to any desired shape to meet the needs of a particular imining operation. For example, where the stratum mined is of limited depth, it will generally be preferred to employ a bladder of greater diameter than height. By the use of a bladder of suitable shape, and particularly by the use of Abladders which may be inated in steps to provide a variety of shapes of increasing volume, the growth of the cavity can be controlled to provide optimum removal of valuable ore between the limiting dimensions of the ore-containing stratum. Thus, in a stratum of shallow depth, a -bladder as aforedescribed capable of cont-rolled expansion in a radial direction can be employed to control the growth of the cavity to provide a final cavity shape compatible with the limited depth of the stratum, but of substantial diameer, Further, the bladder is useful in controlling cavity shape to produce a more nearly cylindrical cavity and to avoid the formation of a cavity of substantially inverted-triangular, vertical cross-section, as frequently otherwise occurs.

While any suitable uid may be used to expand the Ibladder to the desired size, it is preferred to employ a liquid having approximately the same density of the solvent used in the solution mining operation. yIn this way any tendency of the bladder to rise or sag due to differential density effects is avoided.

The invention has been described with reference to a single well solution mining operation for the recovery of valuable minerals. It will be apparent to those skilled in the art that the method and apparatus of this invention are equally applicable to the removal of soluble minerals from subterranean formations to form cavities for the storage of volatile material such as natural gas and LPG, or for the safe disposal of radioactive waste material.

While the invention has been described in detail with reference to the several preferred embodiments thereof, it will be understood that within the scope of the appended claims the invention can be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In the removal of soluble minerals from a subterranean formation by providing an input conduit having an outlet within said formation and an output conduit having an inlet within said formation and spaced from said outlet, and circulating a solvent through said formation between said outlet and inlet, whereby a cavity is formed, the improvement comprising disposing a collapsed, flexible bladder within said cavity between said inlet and outlet and inating said bladder to a size smaller than said cavity to provide a substantial bulk between said outlet and inlet, and continuing the circulation of solvent from said outlet to said inlet over a course defined as lying between said bladder and the periphery of said cavity.

2. The method in accordance with claim 1 wherein said bladder is secured in collapsed condition adjacent the end of one said conduit, and said bladder is disposed in the cavity by passing the one said conduit and bladder through the othe-r said conduit and into the cavity, prior to inflating the bladder.

3. The method in accordance with claim 2 in which the one said conduit is said output conduit and the other said conduit is said input conduit.

4. The method in accordance with claim 3 in which said bladder is inated to occupy a major portion of the volume of said cavity.

5. The method in accordance with claim 3 in which the outlet of said input conduit is connected to the interior of said bladder, said bladder is provided with a plurality of fluid openings disposed remotely with respect to said inlet, and solvent is circulated from said input conduit into said bladder, and out of said uid openings and through the cavity to said inlet.

6. A manufacture comprising a rigid, substantially straight tube section, a bladder fabricated of a foldable, flexible material encompassing a portion of said tube section intermediate the ends thereof, said bladder being secured to said tube section in fluid-tight relationship therewith adjacent one end thereof, a packer secured to said tube section at a point remote from said one end said packer having a greater diameter than the diameter of said bladder when folded, said bladder being secured to said packer in fluid-tight relationship therewith, an opening extending axially through said packer and communicating with the interior of said bladder, said bladder being provided with a plurality of openings therein spaced remotely with respect to the said one end of said tube section.

7. In a system for the removal of soluble minerals from a subterranean formation, a subterranean cavity, Huid distribution means comprising an open casing extending between the surface of the earth and said cavity, said casing terminating a substantial distance above the bottom of said cavity, an open tubing string of smaller diameter than said casing extending through said casing and terminating below the lower end of said casing and within said cavity, a bladder fabricated of a foldable, flexible, substantially fluid impervious material encompassing a portion of said tubing string intermediate the cavity adjacent terminus thereof and said casing, a fluid-tight packer disposed between said casing and said tubing string to form a seal therebetween, said bladder being secured to said packer in uid-tight relationship therewith, an aperture in said packer connecting the interior of said bladder with the interior of said casing above said packer, said bladder being provided with a plurality of openings located remotely with respect to said terminus of said tubing string.

References Cited by the Examiner UNITED STATES PATENTS 1,523,286 1/1925 Railsback 166-187 3,032,115 5/1962 Smith 166-181 3,054,455 9/1962 Keltuer 166-187 ERNEST R. PURSER, Primary Examiner.

vBENJAMIN HERSH, CHARLES E. OCONNELL,

Examiners. 

1. IN THE REMOVAL OF SOLUBLE MINERALS FROM A SUBTERRANEAN FORMATION BY PROVIDING AN INPUT CONDUIT HAVING AN OUTLET WITHIN SAID FORMATION AND AN OUTPUT CONDUIT HAVING AN INLET WITHIN SAID FORMATION AND SPACED FROM SAID OUTLET, AND CIRCULATING A SOLVENT THROUGH SAID FORMATION BETWEEN SAID OUTLET AND INLET, WHEREBY A CAVITY IS FORMED, THE IMPROVEMENT COMPRISING DISPOSING A COLLAPSED, FLEXIBLE BLADDER WITHIN SAID CAVITY BETWEEN SAID 